The wet blasting machine works primarily by blasting a slurry using the force of compressed air. The slurry is sent to the blasting gun by a low-pressure slurry pump, and the slurry after blasting is separated into two parts, solid particles and liquid. An air compressor and a low-pressure slurry pump are indispensable equipment for this machine to operate. Accordingly, the size of the machine becomes large, and its price is expensive.
Applicant, in an attempt to eliminate such disadvantages, has offered a high-water-pressure wet blasting machine in which the clarified water in the clear water tank is sent to the blasting gun by a high-pressure pump and, by ejection of this high-pressure water, slurry in the reclaiming hopper is sucked and is blasted through the blasting gun with the high-pressure water. The blasted slurry is sent to a solid-liquid separator, where the separated solid particles are returned to the reclaiming hopper and other separated liquid is clarified in the clear tank. In this machine, the reclaiming hopper is located lower than the blasting gun, so that the vacuum force generated by the Venturi effect of the blasting gun is used to bring the slurry upwardly from the water level of the reclaiming hopper to the height of the blasting gun. The necessary suction force generated by the Venturi effect must consequently be of large magnitude in order to suck the slurry up from the reclaiming hopper to the gun, and hence the pressure of the clear water supplied to the gun as the ejecting medium needs to be high (such as at least 30 kg/cm.sup.2, or more) so as to create a sufficiently strong suction or Venturi effect.
The present invention relates to improvements in the wet blasting machine so as to improve upon the known operation. More specifically, by use of a third tank or reservoir for abrasive particles positioned substantially at, or above, the elevation of the blasting gun, the water pressure can be substantially reduced while still maintaining the same effective cutting rate. The present invention also permits the successful use of ferrous particles as the blasting medium when water is used as the ejecting medium .